If I connect my 5700 XT to my 4k Samsung TV the screen turns on and off even in desktop mode. During games I can still hear sound but screen goes blank for a couple of seconds then returns.
This has happened across all drivers since launch and even a couple of system formats.
Never had this issue with my Nvidia cards. Tried a few different HDMI cables that all work fine with Nvidia cards too.
Seems to be fixed by enabling GPU Scaling on for all screens connected to card. No issues since I did that.